It is known to label containers with labels that provide consumer information. It is also known to apply individualized marks or other information to containers using ink jet printers in ways that are not permitted by label printing. Known printing systems that can do this work in monochrome and cannot print more than a few printing dots or lines.
It is known, furthermore, that work is in progress on printing methods and systems that make possible printing of widths of up to 174 mm per printing head using printing heads of different manufacturers. These printing heads also work in monochrome.
For multicolor printing, printing heads have to be arranged one after the other and suitably offset so that, depending on the number of colors, an even pitch between individual printing dots is achieved. This is possible with an adjustment on a machine having a plurality of printing heads arranged one after the other in a fixed manner. In these machines, the packaging to be printed upon is moved past the printing heads with constant speed. The performance of such a machine therefore depends on the printing speed of a respective printing head.
Machines along the lines of the foregoing are practicable for printing on absorbent packaging materials. However, if one wishes to print on a non-absorbent material, such as metal, glass or plastic, the ink has to cured between colors, for example by heat drying, or by UV or electron beams through cross-linking. The need to cure between colors increases the length of such machines. If one wishes to increase the performance, either a plurality of printing systems have to be connected in parallel, or a different arrangement has to be selected.
The prior art has also suggested arranging holders on a carousel for packing material to be printed in circular form and rotating the individual packaging itself on the individual station during the rotation of the carousel and thus guiding the surface of the packaging past printing heads arranged on each station and oriented relative to one another. A disadvantage of this is that with surfaces that require the use of inks to be cured by UV or electron beams, no intermediate drying or cross-linking of the individual printing inks is possible.
There is therefore the additional proposal of applying each color on individual carousels arranged one after the other in series, wherein the drying/cross-linking can take place during the transfer between the individual carousels. It is provided, with this embodiment, to fasten the container or the packages on a belt clamped in an independent transport unit, thus moving these in a centered manner one after the other through the various carousels arranged one after the other. This holding device would have to be embodied as a rotary mounting so that the containers drive one another on the carousels and thus are guided past the individual printing head of the respective color with the entire surface.
It was proposed, furthermore, to clamp containers in individual holding devices, wherein each holding device rotatably receives the container and has a marking for the 0 degree angle clamped-in. The containers are individually transported and received with the holding device in printing machines connected in series. Here, the holding device and the mounting are designed so that a centering of the holding device in the machine takes place with such precision that the container is oriented to match the print image of the corresponding printing head and through the 0 degree marking, also matching with respect to the rotary axis.
The requirements of centering and maintaining the accuracy of the guide for achieving a high-quality print image, however, are high. Doing so is a complex undertaking since, during start-up and braking, different tensile forces act on the belt. Temperature fluctuations can additionally occur. Both of these effects can lead to tolerances being exceeded to the point where they cannot be compensated for. To make matters worse, a container can sometimes be quite heavy. For example, when the container is a bottle, the printing normally takes place after the bottle has been filled. Added to all this weight is the mass of the holding device itself.
The precision of the centering requirement becomes clear when one knows that with the usual 600 dpi of printing quality, the printing dots are 0.042 mm apart from one another. This means that a holding device that is holding a rather heavy bottle filled with liquid has to somehow be permanently aligned to 1/100 mm. With processing quantities of, for example, 36,000 bottles/hour in the beverage industry, more than 200,000,000 bottles pass through such a machine in a year. Because of this, the wear is huge, and substantially influences the printing quality.